The present disclosure relates to image reading devices.
Electronic copiers, facsimile machines, etc. are known as image forming apparatuses including an original document reading device that reads an original document, such as a photograph, a document, or the like placed on a platen glass. It is known that such an image forming apparatus first determines the size of an original document placed on the platen glass and performs then control on reading, selection of paper to be printed, etc. on the basis of the determined original document size.
In order to determine the original document size, it is proposed to utilize image data read by a scanner that reads an original document. One type of the image forming apparatus is provided with an opening/closing detection means that detects opening/closing of a platen cover in a two-step manner. When a state in which the platen cover is being closed is detected, first scan is performed. When a state in which the platen cover is closed fully is detected, second scan is performed. On the basis of line sensor output obtained by the two-time scan, the original document size is determined